CELLULAR WHEEL AND METHOD FOR THE PRODUCTION THEREOF
A cellular wheel made of metal comprises an outer sleeve located symmetrically to a rotational axis and an inner sleeve. The annular space between the outer sleeve and inner sleeve is divided by cell wall parts, which are oriented in parallel to the rotational axis and delimited by cell edges, into a plurality of rotation-symmetrically arranged cells, wherein the cell edges are located on intersecting lines of cylinder lateral surfaces with rotation-symmetrically arranged axial planes, said surfaces being arranged concentrically to the rotational axis. The outer sleeve and inner sleeve delimit a cell structure, in which cell edges, which delimit a cell wall part in each case, are concurrently located in pairs on adjoining cylinder lateral surfaces and on adjoining axial planes. With each cell edge located on two adjoining axial planes of adjoining cylinder lateral surfaces, each cell edge on a cylinder lateral surface delimits two cell walls.
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The present invention relates to a cellular wheel made of metal, comprising a cylindrical outer sleeve located symmetrically to a rotational axis and a cylindrical inner sleeve located concentrically to the outer sleeve, wherein the space between the outer sleeve and the inner sleeve is divided into a multiplicity of rotation-symmetrically arranged cells by cell wall parts delimited by cell edges oriented parallel to the rotational axis, which cell edges lie with rotation-symmetrically arranged axial planes on lines of intersection of cylinder shell surfaces arranged concentrically to the rotational axis. A method suitable for producing the cellular wheel also lies within the scope of the invention.
PRIOR ARTFor some years, the process of downsizing has been one of the key issues in the design of new, supercharged engines. With downsizing, the fuel consumption and thus the exhaust emissions of a vehicle can be reduced. These aims are nowadays becoming increasingly important, since the high energy consumption by fossil fuels contributes strongly to air pollution and increasingly strict legislative measures are forcing automobile manufacturers to take action. By downsizing, the substitution of a high-volume engine by a reduced-capacity engine is understood. In this way, the engine power should be maintained at a constant rate by charging the engine. The aim is to achieve the same output values with low-volume engines as with equally powerful naturally aspirated engines. New insights in the field of downsizing have shown that, particularly in very small Otto engines with a cubic capacity of 1 liter or less, the best results can be obtained with pressure wave supercharging.
In a pressure wave supercharger, the rotor is configured as a cellular wheel and is enclosed by an air and exhaust housing having a common casing. The development of modern pressure wave superchargers for supercharging small engines leads to cellular wheels having a diameter in the order of magnitude of 100 mm or less. In order to obtain a maximum cell volume and also reduce the weight, cell wall thicknesses of 0.2 mm or less are aimed for. Given the high exhaust inlet temperatures of around 1000° C., virtually only high-temperature steels can be considered as materials for the cellular wheel. The production of dimensionally stable and high-precision cellular wheels with low cellular wall thickness is today barely possible, or else is associated with considerable additional costs.
It has already been proposed to form the chambers of a cellular wheel from aligned and partially overlapping, Z-shaped profiles. The production of such a cellular wheel is associated, however, with high time expenditure. Added to this is the fact that the alignment and positionally accurate fixing of Z-profiles is barely practicable with a precision sufficient to meet the required tolerances.
It has already been proposed to produce a cellular wheel from a solid body by erosion of the individual cells. With this method, it is not possible, however, to achieve cell wall thicknesses of 0.2 mm. A further fundamental drawback of the erosion method is constituted by the high material and machining costs associated therewith.
From EP-A-1 375 859, a cellular wheel of the type stated in the introduction is known. The cellular wheel comprises an outer sleeve, an inner sleeve located concentrically to the outer sleeve and an intermediate sleeve arranged between the outer sleeve and the inner sleeve concentrically to these same. Between the outer sleeve and the intermediate sleeve and between the intermediate sleeve and the inner sleeve are arranged blades oriented radially to the rotational axis. The individual cells are delimited by two adjacent blades and adjacent sleeves. In load tests under practical conditions, it has been shown that, particularly with cell wall thicknesses of 0.5. mm or less, a torsion of the sleeves and a vibration of the blades occur. This unstable behavior leads after a short while to failure of the cellular wheel.
REPRESENTATION OF THE INVENTIONThe object of the invention is to provide a cellular wheel of the type stated in the introduction, which has a higher rigidity than cellular wheels according to the prior art, given comparable cell wall thickness. Moreover, the cellular wheel is designed to be able to be produced in a simple and cost-effective manner with the required precision, while avoiding the drawbacks of the prior art. A further aim of the invention is to provide a dimensionally stable, lightweight cellular wheel for use in a pressure wave supercharger for supercharging internal combustion engines, in particular for supercharging small Otto engines having a cubic capacity in the order of magnitude of 1 liter or less. A still further aim of the invention is to provide a method for the cost-effective production of dimensionally stable and high-precision cellular wheels having a cell wall thickness of 0.4 mm or less.
In a cellular wheel of the type stated in the introduction, the inventive solution of the object is achieved by the fact that the outer sleeve and the inner sleeve delimit a cell structure constructed from a network formed in cross section in mesh-like arrangement from connected cell wall parts, in which cell structure cell edges, which in pairs respectively delimit a cell wall part, lie simultaneously on adjacent cylinder shell surfaces and on adjacent axial planes, wherein each cell edge on a cylinder shell surface, with each of the cell edges lying on two adjacent axial planes of an adjacent cylinder shell surface, respectively delimits two cell wall parts.
By virtue of the cell structure which is used according to the invention, the cellular wheel has a substantially higher rigidity than the known cellular wheels. Moreover, the absence of intermediate sleeves leads, in addition to a considerable weight reduction, to a strongly increased passage cross section.
The cell structure preferably comprises three or four cylinder shell surfaces, though cellular wheels having more than four cylinder shell surfaces are also conceivable.
In a particularly preferred, cost-effective method for producing the cellular wheel according to the invention, the cell structure is formed, based on the industrial production of honeycomb structures, by stretching of blade assemblies made up of blades connected locally at different points.
The method is distinguished by the following steps to be executed in sequence:
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- (a) provision of a predefined number of blades having a length corresponding to the length of the cellular wheel and a width appropriately tailored to the predefined thickness of the annular space between the outer sleeve and the inner sleeve;
- (b) paired welding together of the blades in the longitudinal direction at predefined points to form a blade assembly, with the formation of the cell edges;
- (c) stretching of the blade assembly in a direction perpendicular to the plane of the blades and of the stretched blade assembly to form the annular cell structure;
- (d) connection of the two terminal blades of the stretched and bent blade assembly along corresponding cell edges;
- (e) sliding of the inner sleeve into the annular cell structure and sliding of the outer sleeve onto the annular cell structure;
- (f) connection of the outer sleeve and inner sleeve to the blade edges.
The connection of the two terminal blades of the stretched and bent blade assembly along corresponding cell edges, and the connection of the outer sleeve and inner sleeve to the blade edges, is preferably carried out by welding together the parts by means of a laser beam or electron beam.
A further preferred method for producing the cellular wheel according to the invention is distinguished by the following steps to be executed in sequence:
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- (a) provision of a predefined number of blades having a length corresponding to the length of the cellular wheel and a width appropriately tailored to the predefined thickness of the annular space between the outer sleeve and the inner sleeve;
- (b) shaping of the blades in accordance with their definitive shape predefined by the annular cell structure and, if necessary, connection of blade pairs to form individual cells;
- (c) placement of the shaped blades or the cells at predefined points in a predefined number on the outer side of the inner sleeve, and connection of the blades or the cells one to another to form the annular cell structure, and to the inner sleeve;
- (d) sliding of the outer sleeve onto the annular cell structure;
- (f) connection of the outer sleeve and inner sleeve to the blade edges.
The connection of the blade pairs to form individual cells, and the connection of the blades or the cells one to another to form the annular cell structure, and to the inner sleeve, is preferably carried out by welding together the parts by means of a laser beam or electron beam.
The cellular wheel produced with the method according to the invention is preferably used in a pressure wave supercharger for supercharging internal combustion engines, in particular Otto engines having a cubic capacity of 1 liter or less.
Further advantages, features and details of the invention emerge from the following description of preferred illustrative embodiments and with reference to the drawing, which serves merely for illustrative purposes and should not be construed restrictively. The drawing shows schematically in
A cellular wheel 10, shown in
In the cellular wheel 10 shown in
In the cellular wheel 10 shown in
The cellular wheel 10 represented by way of example in
The production of a cellular wheel is explained in greater detail in the following description of illustrative embodiments.
As can be seen from
The blades 16 are lamellar, flat sheet-metal parts and are usually cut to the predefined length from a sheet-metal strip which is present in roll form.
The length 1 of the blades corresponds to the length L of the cellular wheel 10. The width b of the blades 16 or of the blade assembly 26 is greater than the width or thickness B of the annular space or of the annular cell structure 17 between the outer sleeve 12 and the inner sleeve 14 and allows for the decrease in width b of the blade assembly 26 which occurs when the blade assembly 26 is subsequently stretched and bent into the cell structure 17.
For the formation of the cell structure 17 represented in
In a next step, the outer sleeve 12 and the inner sleeve 14 in the form of tubular sleeves are slid on or in from a front face. Prior to the performance of the welding operation, the cell walls of the annularly bent cell structure 17 are fixed in the predefined angular position in a positionally accurate manner by means of frontally inserted tools. Following the positioning of the outer sleeve 12 and the inner sleeve 14, the longitudinal edges 16k of the welded-together blade pairs 16 are welded to the outer sleeve 12 or the inner sleeve 14 through the outer sleeve 12 or the inner sleeve 14 by means of a laser beam guided along each longitudinal edge 16k (
For the formation of the cell structure 17 represented in
In a next step, the outer sleeve 12 and the inner sleeve 14 in the form of tubular sleeves are slid on or in from a front face. Prior to the performance of the welding operation, the cell walls of the annularly bent cell structure 17 are fixed in the predefined angular position in a positionally accurate manner by means of frontally inserted tools 34. Following the positioning of the outer sleeve 12 and the inner sleeve 14, the longitudinal edges 16k of the welded-together blade pairs 16 are welded to the outer sleeve 12 or the inner sleeve 14 through the outer sleeve 12 or the inner sleeve 14 by means of a laser beam guided along each longitudinal edge 16k (
A comparison of
In the paired welding of the blades 16 to form the blade assembly 26, all weld seams can be made with a laser beam guided perpendicular to the plane of the blades 16 (
As can be seen from
The connection of the inner sleeve 14 to the flanged sleeve 15 can be effected, for instance, by welding together the end edges of the inner sleeve 14 and the flanged sleeve 15 by means of laser beams 30 (not represented in the drawing).
As shown in
10 cellular wheel
12 outer sleeve
13 drive shaft
14 inner sleeve
15 flanged sleeve
16 blades
17 cell structure
18a,18b,18c cylinder shell surface
19 cell wall part
20 cell edges
21 axial plane
22,22a,22b,22′,22″ cells
24 labyrinth cell part
26 blade assembly
30,30′,30″ laser beam
34 tool
y rotational axis
Claims
1. A cellular wheel made of metal, comprising:
- a cylindrical outer sleeve located symmetrically with respect to a rotational axis (y), and
- a cylindrical inner sleeve located concentrically with respect to the outer sleeve,
- wherein an annular space between the outer sleeve and the inner sleeve is divided into a multiplicity of rotation-symmetrically arranged cells by cell wall parts delimited by cell edges oriented parallel to the rotational axis (y), which cell edges lie with rotation-symmetrically arranged axial planes on lines of intersection of cylinder shell surfaces arranged concentrically to the rotational axis (y),
- wherein the outer sleeve and the inner sleeve delimit a cell structure constructed from a network formed in cross section in mesh-like arrangement from connected cell wall parts, in which cell structure cell edges, which in pairs respectively delimit a cell wall part, lie simultaneously on adjacent cylinder shell surfaces and on adjacent axial planes, and
- wherein each cell edge on a cylinder shell surface, with each of the cell edges lying on two adjacent axial planes of an adjacent cylinder shell surface, respectively delimits two cell wall parts.
2. The cellular wheel as claimed in claim 1, wherein the cell structure comprises three cylinder shell surfaces.
3. The cellular wheel as claimed in claim 1, wherein the cell structure comprises four cylinder shell surfaces.
4. The cellular wheel as claimed in claim 1, wherein the cell structure comprises more than four cylinder shell surfaces.
5. The cellular wheel as claimed in claim 1, wherein the wall thickness of the materials used to produce the cellular wheel measures 0.4 mm or less.
6. A method for producing from metal a cellular wheel, comprising:
- a cylindrical outer sleeve located symmetrically with respect to a rotational axis (y), and
- a cylindrical inner sleeve located concentrically with respect to the outer sleeve,
- wherein an annular space between the outer sleeve and the inner sleeve is divided into a multiplicity of rotation-symmetrically arranged cells by cell wall parts delimited by cell edges oriented parallel to the rotational axis (y), which cell edges lie with rotation-symmetrically arranged axial planes on lines of intersection of cylinder shell surfaces arranged concentrically to the rotational axis (y),
- wherein the method comprises the following steps to be executed in sequence;
- (a) provision of a predefined number of blades having a length (l) corresponding to the length (L) of the cellular wheel and a width (b) appropriately tailored to the predefined thickness (B) of the annular space between the outer sleeve and the inner sleeve;
- (b) paired welding together of the blades in the longitudinal direction at predefined points to form a blade assembly, with the formation of the cell edges;
- (c) stretching of the blade assembly in a direction (z) perpendicular to the plane of the blades and of the stretched blade assembly to form the annular cell structure;
- (d) connection of the two terminal blades of the stretched and bent blade assembly along corresponding cell edges;
- (e) sliding of the inner sleeve into the annular cell structure and sliding of the outer sleeve onto the annular cell structure;
- (f) connection of the outer sleeve and inner sleeve to the blade edges.
7. The method as claimed in claim 6, wherein the connection of the two terminal blades of the stretched and bent blade assembly along corresponding cell edges and the connection of the outer sleeve and inner sleeve to the blade edges, is carried out by welding together the parts by means of a laser beam or electron beam.
8. A method for producing from metal a cellular wheel, comprising:
- a cylindrical outer sleeve located symmetrically with respect to a rotational axis (y), and
- a cylindrical inner sleeve located concentrically with respect to the outer sleeve,
- wherein an annular space between the outer sleeve and the inner sleeve is divided into a multiplicity of rotation-symmetrically arranged cells by cell wall parts delimited by cell edges oriented parallel to the rotational axis (y), which cell edges lie with rotation-symmetrically arranged axial planes on lines of intersection of cylinder shell surfaces arranged concentrically to the rotational axis (y),
- wherein the method comprises the following the steps to be executed in sequence (a) provision of a predefined number of blades having a length (l) corresponding to the length (L) of the cellular wheel and a width (b) appropriately tailored to the predefined thickness (B) of the annular space between the outer sleeve and the inner sleeve;
- (b) shaping of the blades in accordance with their definitive shape predefined by the annular cell structure and, if necessary, connection of blade pairs to form individual cells;
- (c) placement of the shaped blades or the cells at predefined points in a predefined number on the outer side of the inner sleeve, and connection of the blades or the cells one to another to form the annular cell structure and to the inner sleeve;
- (d) sliding of the outer sleeve onto the annular cell structure;
- (e) connection of the outer sleeve and inner sleeve to the blade edges.
9. A method as claimed in claim 8, characterized in that wherein the connection of the blade pairs to form individual cells, and the connection of the blades or the cells one to another to form the annular cell structure, and to the inner sleeve, is carried out by welding together the parts by means of a laser beam or electron beam.
10. The use of a cellular wheel as claimed in claim 1 in a pressure wave supercharger for supercharging internal combustion engines.
11. The use of a cellular wheel as claimed in claim 2 in a pressure wave supercharger for supercharging internal combustion engines.
12. The use of a cellular wheel as claimed in claim 3 in a pressure wave supercharger for supercharging internal combustion engines.
13. The use of a cellular wheel as claimed in claim 4 in a pressure wave supercharger for supercharging internal combustion engines.
14. The use of a cellular wheel as claimed in claim 5 in a pressure wave supercharger for supercharging internal combustion engines.
Type: Application
Filed: Apr 27, 2010
Publication Date: Mar 8, 2012
Applicant: MEC Lasertec AG (Leimbach)
Inventor: Karl Merz (Reinach)
Application Number: 13/318,656
International Classification: F04F 13/00 (20090101); B21D 53/26 (20060101);